Soil Profiles: Nitrogen Conversion and Salt Motility Altered by Feedlot Manure Management

Abstract

AbstractTwo manure management plans were successively imposed on soil profile combinations of clay loam, sand, clay loam over sand, and sand over clay loam to study salt movement and nitrogen (N) transformations in a beef cattle feedlot. These soils were placed in replicated lysimeters located in each of two areas of a feedlot stocked at the rate of one animal, weighing 270 to 450 kg, per 15.2 m2. After loading the soils with N, including nitrate nitrogen (NO−3‐N), by means of a manure‐sawdust mulch for 4 yr (first manure management plan), cores were removed for physical and chemical analyses. Then, the mulch was changed to an intact‐manure pack for 2.5 yr (second manure management plan) which was followed by a second coring and soil analyses. Each management plan and profile combination affected salt movement and N transformations differently. The intact‐manure pack decreased soil profile water and NO−3‐N contents, and increased ammonium N in that part of the soil profile near the manure‐soil interface. Clay loam over clay loam retained more salt but was slower than sand over sand in promoting desired changes and decrease of NO−3‐N. The other profile configurations had similar effects related to texture. The interaction effects of management by location or management by location by soil in either upper or lower fills were not important variables influencing shifts of soil characteristics.